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Table 3 Rotated factor loadings of the factors of the original items of the 15D questionnaires and the AQ20 questionnaire.

From: Comparison between the disease-specific Airways Questionnaire 20 and the generic 15D instruments in COPD

15D questionnaire

AQ20 questionnaire

Name of the factor

Original item

Rotated factor loadings

Name of the factor

Original item

Rotated factor loadings

"Limitation in physical activity" (15.7% of the variation)

Usual activities

Breathing

Mobility

Vitality

Sexual activity

0.77

0.75

0.66

0.55

0.47

"Limitation in physical activity" (13.3% of the variation)

AQ3

AQ13

AQ11

AQ12

AQ17

0.76

0.70

0.64

0.49

0.48

"Psychic wellbeing" (14.7% of the variation)

Depression

Distress

Vitality

0.89

0.79

0.54

"Symptoms at rest" (10.2% of the variation)

AQ5

AQ18

AQ9

AQ19

AQ7

0.56

0.48

0.47

0.44

0.42

"Capability of thinking and speaking" (8.1% of the variation)

Mental functions

Speech

0.55

0.42

"Emotional concern" (8.9% of the variation)

AQ2

AQ16

AQ20

AQ6

AQ17

0.58

0.55

0.54

0.45

0.44

Eating (3.9% of the variation)

Eating

0.40

"Limitations in daily activities" (6.0% of the variation)

AQ14

AQ10

AQ15

0.57

0.43

0.41

  1. All factors with eigenvalues more >1 and factor loading ≥0.4 were included, maximum likelihood was chosen as the extraction method. The rotational method used was orthogonal, e.g. Varimax.